Abstract
Using a multistep synthetic pathway, a bis(imino)pyridine (or pyridine diimine, PDI) molybdenum catalyst for the selective conversion of carbon dioxide into methanol has been developed. Starting from (Ph2PPrPDI)Mo(CO), I2 addition afforded [(Ph2PPrPDI)MoI(CO)][I], which features a seven-coordinate Mo(II) center. Heating this complex to 100°C under vacuum resulted in CO loss and the formation of [(Ph2PPrPDI)MoI][I]. Reduction of [(Ph2PPrPDI)MoI][I] in the presence of excess K/Hg yielded (κ6-P,N,N,N,C,P-Ph2PPrPDI)MoH following methylene group C-H activation at the α-position of one PDI imine substituent. The addition of CO2 to (κ6-P,N,N,N,C,P-Ph2PPrPDI)MoH resulted in facile insertion to generate the respective η1-formate complex, (κ6-P,N,N,N,C,P-Ph2PPrPDI)Mo(OCOH). When low pressures of CO2 were added to solutions of (κ6-P,N,N,N,C,P-Ph2PPrPDI)MoH containing pinacolborane, the selective formation of H3COBPin and O(BPin)2 was observed along with precatalyst regeneration. When HBPin was limited, H2C(OBPin)2 was observed as an intermediate and (κ6-P,N,N,N,C,P-Ph2PPrPDI)Mo(OCOH) remained present throughout CO2 reduction. The hydroboration of CO2 to H3COBPin was optimized and 97% HBPin utilization by 0.1 mol % (κ6-P,N,N,N,C,P-Ph2PPrPDI)MoH was demonstrated over 8 h at 90°C, resulting in a methoxide formation turnover frequency (TOF) of 40.4 h-1 (B-H utilization TOF = 121.2 h-1). Hydrolysis of the products and distillation at 65°C allowed for MeOH isolation. The mechanism of (κ6-P,N,N,N,C,P-Ph2PPrPDI)MoH mediated CO2 hydroboration is presented in the context of these experimental observations. Notably, (κ6-P,N,N,N,C,P-Ph2PPrPDI)MoH is the first Mo hydroboration catalyst capable of converting CO2 to MeOH, and the importance of this study as it relates to previously described catalysts is discussed.
| Original language | English |
|---|---|
| Pages (from-to) | 7506-7515 |
| Number of pages | 10 |
| Journal | Inorganic Chemistry |
| Volume | 54 |
| Issue number | 15 |
| DOIs | |
| Publication status | Published - Aug 3 2015 |
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ASJC Scopus subject areas
- Inorganic Chemistry
- Physical and Theoretical Chemistry
Cite this
Conversion of Carbon Dioxide to Methanol Using a C-H Activated Bis(imino)pyridine Molybdenum Hydroboration Catalyst. / Pal, Raja; Groy, Thomas L.; Trovitch, Ryan.
In: Inorganic Chemistry, Vol. 54, No. 15, 03.08.2015, p. 7506-7515.Research output: Contribution to journal › Article
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TY - JOUR
T1 - Conversion of Carbon Dioxide to Methanol Using a C-H Activated Bis(imino)pyridine Molybdenum Hydroboration Catalyst
AU - Pal, Raja
AU - Groy, Thomas L.
AU - Trovitch, Ryan
PY - 2015/8/3
Y1 - 2015/8/3
N2 - Using a multistep synthetic pathway, a bis(imino)pyridine (or pyridine diimine, PDI) molybdenum catalyst for the selective conversion of carbon dioxide into methanol has been developed. Starting from (Ph2PPrPDI)Mo(CO), I2 addition afforded [(Ph2PPrPDI)MoI(CO)][I], which features a seven-coordinate Mo(II) center. Heating this complex to 100°C under vacuum resulted in CO loss and the formation of [(Ph2PPrPDI)MoI][I]. Reduction of [(Ph2PPrPDI)MoI][I] in the presence of excess K/Hg yielded (κ6-P,N,N,N,C,P-Ph2PPrPDI)MoH following methylene group C-H activation at the α-position of one PDI imine substituent. The addition of CO2 to (κ6-P,N,N,N,C,P-Ph2PPrPDI)MoH resulted in facile insertion to generate the respective η1-formate complex, (κ6-P,N,N,N,C,P-Ph2PPrPDI)Mo(OCOH). When low pressures of CO2 were added to solutions of (κ6-P,N,N,N,C,P-Ph2PPrPDI)MoH containing pinacolborane, the selective formation of H3COBPin and O(BPin)2 was observed along with precatalyst regeneration. When HBPin was limited, H2C(OBPin)2 was observed as an intermediate and (κ6-P,N,N,N,C,P-Ph2PPrPDI)Mo(OCOH) remained present throughout CO2 reduction. The hydroboration of CO2 to H3COBPin was optimized and 97% HBPin utilization by 0.1 mol % (κ6-P,N,N,N,C,P-Ph2PPrPDI)MoH was demonstrated over 8 h at 90°C, resulting in a methoxide formation turnover frequency (TOF) of 40.4 h-1 (B-H utilization TOF = 121.2 h-1). Hydrolysis of the products and distillation at 65°C allowed for MeOH isolation. The mechanism of (κ6-P,N,N,N,C,P-Ph2PPrPDI)MoH mediated CO2 hydroboration is presented in the context of these experimental observations. Notably, (κ6-P,N,N,N,C,P-Ph2PPrPDI)MoH is the first Mo hydroboration catalyst capable of converting CO2 to MeOH, and the importance of this study as it relates to previously described catalysts is discussed.
AB - Using a multistep synthetic pathway, a bis(imino)pyridine (or pyridine diimine, PDI) molybdenum catalyst for the selective conversion of carbon dioxide into methanol has been developed. Starting from (Ph2PPrPDI)Mo(CO), I2 addition afforded [(Ph2PPrPDI)MoI(CO)][I], which features a seven-coordinate Mo(II) center. Heating this complex to 100°C under vacuum resulted in CO loss and the formation of [(Ph2PPrPDI)MoI][I]. Reduction of [(Ph2PPrPDI)MoI][I] in the presence of excess K/Hg yielded (κ6-P,N,N,N,C,P-Ph2PPrPDI)MoH following methylene group C-H activation at the α-position of one PDI imine substituent. The addition of CO2 to (κ6-P,N,N,N,C,P-Ph2PPrPDI)MoH resulted in facile insertion to generate the respective η1-formate complex, (κ6-P,N,N,N,C,P-Ph2PPrPDI)Mo(OCOH). When low pressures of CO2 were added to solutions of (κ6-P,N,N,N,C,P-Ph2PPrPDI)MoH containing pinacolborane, the selective formation of H3COBPin and O(BPin)2 was observed along with precatalyst regeneration. When HBPin was limited, H2C(OBPin)2 was observed as an intermediate and (κ6-P,N,N,N,C,P-Ph2PPrPDI)Mo(OCOH) remained present throughout CO2 reduction. The hydroboration of CO2 to H3COBPin was optimized and 97% HBPin utilization by 0.1 mol % (κ6-P,N,N,N,C,P-Ph2PPrPDI)MoH was demonstrated over 8 h at 90°C, resulting in a methoxide formation turnover frequency (TOF) of 40.4 h-1 (B-H utilization TOF = 121.2 h-1). Hydrolysis of the products and distillation at 65°C allowed for MeOH isolation. The mechanism of (κ6-P,N,N,N,C,P-Ph2PPrPDI)MoH mediated CO2 hydroboration is presented in the context of these experimental observations. Notably, (κ6-P,N,N,N,C,P-Ph2PPrPDI)MoH is the first Mo hydroboration catalyst capable of converting CO2 to MeOH, and the importance of this study as it relates to previously described catalysts is discussed.
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U2 - 10.1021/acs.inorgchem.5b01102
DO - 10.1021/acs.inorgchem.5b01102
M3 - Article
VL - 54
SP - 7506
EP - 7515
JO - Inorganic Chemistry
JF - Inorganic Chemistry
SN - 0020-1669
IS - 15
ER -